A FUNDAMENTAL-STUDY ON IMPACT DAMPERS

A fundamental study on impact dampers is reported in which the performance of impact dampers was investigated from free damped vibration generated when a step function input was supplied to a leaf spring with a free mass. The investigation showed that the damping capability of impact dampers results from collision between the free mass and the main mass. The frequency of the system with an impact damper varies with the natural frequency of the main vibratory system and the mass ratio. The optimum damping effect is achieved in combinations of the mass ratio and a clearance, i.e. motion extent of the free mass. The use of a free mass of only 25% of the main mass and a clearance of 0.6 mm, for example, can improve the damping capability of the main vibratory system at least 10 times or more, even though the clearance and the free mass are not adjusted to an amplitude of the main vibratory system. The critical amplitude where the impact damper does not function is determined by the natural frequency and the acceleration of gravity.